Patent GB-739422-A (GB)
Title: Improvements in radio navigation systems
Inventor: MCMULLIN TERENCE ALEXANDER
IPC: G01S1/02
Filed: 1954-02-09
Abstract: 739,422. Radio navigation. MURPHY RADIO, Ltd. Feb. 9, 1954, No. 3841/54. Class 40 (7). The invention relates to receiving equipment for use with an overlapping beam beacon which, in response to interrogating pulses, radiates a succession of pulses of short duration on one beam followed by a succession of pulses of longer duration on the other. According to the invention such equipment includes an amplitude discriminating circuit in which the received pulses produce voltages proportional to their amplitude and prolonged in duration and two integrating circuits feeding an indicator in opposition to each other to which the voltages are fed in turn by a switching arrangement controlled by the received pulses, those arising from the short pulses being fed to one integrator and those from the longer pulses to the other. In one embodiment received signal pulses are applied at A and through capacitor 1 to the grid of pentode 2. In certain arrangements stroke selector pulses may also be fed to valve 2 over capacitor 3. Negative pulses produced at B are fed through transformer 5 to give positive pulses at the anode of diode 8. Each pulse passing through 8 quickly charges capacitor 16 and the charge then leaks away through resistor 15. The time constant of units 15 and 16 is made more than the interval between received pulses but small compared with the period of a group of dots and dashes. The voltage at C is fed to the movable contact 10 of relay 11. This relay directs the signal either over contact 12 to the grid of valve 18 or over contact 13 to the grid valve 19. Capacitors 22 are provided between the anodes and grids of these valves and the indicator 25 connected between the cathodes. This may be a. centre zero meter. Gain control voltage may be derived at C and if the time constant of circuit 15, 16 is such that the voltages generated are affected by the length of the applied pulses the latter may be differentiated. Switching of the dot produced voltages on the one hand and the dash produced voltages on the other to the two sides of the comparision circuit is effected by the relay control circuit fed at E with negative received pulses. These pulses serve to cut off normally conducting diode 27. This gives rise to negative going sawtooth pulses at F which reach a potential below that at the anode of diode 33 only when longer pulses are received. Thus longer pulses only give rise to pulses at G which trigger single stroke multi-vibrator 37, 38 to energize relay 11 for rather less than the interval between the received pulses. Capacitor 39 maintains it so that it is retained and only released if the subsequent dash does not arrive. Another arrangement, including the use of single stroke multivibrator, for obtaining the voltage at point C for application to the switch relay is described with reference to Fig. 3 (not shown). There is also described an improved switch control arrangement involving the use of a polarized relay and a bistable multivibrator with reference to Figs. 4 and 5 (not shown). In this arrangement each dot serves to trigger the multivibrator to one of its stable states and each dash to trigger it to the other so that certain errors due to missing pulses are avoided. Specifications 690,477 and 690,480 are referred to.